Indoor positioning services refer to methods where networks of devices and algorithms are used to locate mobile devices within buildings. Indoor positioning is regarded as a key component of location-aware mobile computing and is an important element in providing augmented reality (AR) services. Location aware computing refers to applications that utilize a user's location to provide content relevant to that location. AR is a technology that overlays a virtual space onto a real (physical) space. To successfully enable AR and location aware computing, accurate indoor positioning is an important requirement.
The Global Positioning System (GPS) loses significant power when it is used indoor as most construction materials shield the satellite signals necessary for positioning by GPS. Additionally, when indoors, GPS suffers from multi-path propagation effects. Alternative solutions for indoor positioning have been sought such as techniques based on received signal strength indication (RSSI) from Wi-Fi and Bluetooth wireless access points, Ultrasonic techniques (US) and optical indoor positioning techniques.
The accuracy of positioning systems based on RSSI is limited as indoor environments cause radio waves to propagate in dynamic and unpredictable ways. Ultrasonic techniques (US) transmit acoustic waves to microphones and operate at lower frequencies than systems based on RSSI from Wi-Fi and Bluetooth. Therefore, signals attenuate significantly when passing through walls which potentially makes US techniques more accurate than systems based on RSSI as signals of adjacent rooms will not interfere.
Optical indoor positioning techniques use optical signals, either visible or infrared, to accurately locate mobile devices indoors. These can be more accurate than the other approaches mentioned, since optical signals are highly directional and typically cannot penetrate solid objects. However, this directionality limits the potential reliability of optical signals, since difficulties in aligning the receiver and transmitter can occur. Conventional optical indoor positioning techniques need, among other things, at least three luminaires in their field of view to work accurately. An example of such an optical indoor positioning technique is discussed in patent application US20140280316.
Thus, there is a need for an optical indoor positioning technique that eliminates the need for careful alignment between receiver and transmitters.